Combustion system



May 11, P. PROBERT ETAL COMBUSTION SYSTEM 3 Sheets-Sheet 1 Original Filed March 22. 1957 pro 691 7 e. e WarZ 2: Eda 4w! /rzg j/e Inveiztazs By Attorrleys May 11, 1965 R. P. PROBERT ETAL 3,182,453

COMBUSTION SYSTEM Original Filed March 22. 1957 s Sheets-Sheet 2 Attorney United States Patent COMBUSTIQN SYSTEM Rhys Price Probert, Farnborough, Peter Martin, Farnham, and Edward Langford Hartley, Farnborough, England, assignors, by mesne assignments, to Power Jets (Research and Development) Limited, London, England, a British company Original application Mar. 22, 1957, Ser. No. 647,918, now Patent No. 3,126,705, dated Mar. 31, 19.64. Divided and this application Oct. 4, 1961, Ser. No. 142,739 Claims priority, application Great Britain, Mar. 26, 1956, 9,313/56 Claims. (Cl. Gil-39.66)

This invention relates to combustion apparatus particularly for use in gas turbine plant. In conventional gas turbine plant in which a compressor discharges a stream of air into a combustionchamber wherein fuel is burnt in the air stream and the combustion gases so produced are discharged through a turbine which drives the compressor, the length of the flow path between the compressor and the turbine is determined partly by the means used for atomisation of the fuel and mixing of the fuel with the air stream in the combustion chamber, and partly by the degree of diffusion required between the compressor air outlet and the combustion chamber air inlet. If such diffusion could be dispensed with a reduction in the length of the said flow path could be made. This would however involve an air velocity at the combustion chamber inlet which is impracticable with the combustion apparatus in general use at present.

In most conventional forms of gas turbine plant the combustion chamber comprises a perforated flame tube and an outer wall Which forms with the flame tube a duct for secondary air. The secondary air flowing in this duct passes through the perforations in the flame tube along its length and mixes with the combustion gases within the flame tube. The length of such combustion chamber is therefore dependent at least partly on the degree of mixing of gases and air required befor they enter the turbine.

According to the present invention, the combustion chamber has a substantially imperforate flame tube surrounded by a casing and secondary air flowing between the flame tube and the casing is mixed with the combustion gases between the inlet guide vanes of the turbine; in this way a reduction may be effected both in the length of the combustion chamber and in the pressure losses within the chamber. In addition, by directing the secondary air on to these guide vanes, cooling of the vane is effected.

Two specific embodiments of the present invention as applied to a gas turbine jet propulsion plant are shown in the accompanying drawings in which:

FIGURE 1 is a diagrammatic side view of a gas turbine jet propulsion plant.

FIGURE 2 is a longitudinal half-sectional view showing in detail part of the gas turbine plant of FIGURE 1.

FIGURES 3, 4 and 5 are sections on the lines IIIIII, 1V-IV, and VV respectively of FIGURE 2 and FIGURE 6 is a view, corresponding to the view shown in FIGURE 2, of an alternative form of combustion means.

FIGURE 7 is a section on the line VII-VII of FIGURE 6.

' The gas turbine shown in FIGURE 1 has an axial-flow compressor 1 receiving air from atmosphere through an annular intake 2, an annular combustion chamber 3 into which the compressor discharges air under compression, an axial-flow turbine 4 connected to receive combustion gases from the combustion chamber and secondary air from the compressor, and a jet pipe 5 through which the turbine exhaust gases discharge to atmosphere as a propulsive jet. The compressor comprises stator blade 6 sup- 3,l82,453 Patented May 11, 1965 1 ice ported on a stator casing 7 and rotor blades 8 supported on a rotor body 9, and similarly the turbine comprises stator blades 10 supported on a stator casing 11 and rotor blades 12 supported on a rotor disc 13, the compressor rotor body and the turbine rotor disc being connected by a shaft 14 which extends along the axis of the plant. This rotor structure is supported on the axis of the plant on a front bearing 15, a rear bearing 16 and in certain instances by an intermediate bearing 17, although it is envisaged that by suitable dimensioning of components this intermediate bearing may be omitted. Fuel is introduced into the combustion chamber from a fuel tank 18 through a control valve 19, a pump 20, a first fuel pipe 21 which extends across the air intake and terminates in a rotary seal 22, a second fuel pipe 23 which extends from the rotary seal axially through the compressor rotor, and a fuel-carrying disc 24 mounted for rotation with the shaft on to the surface of which fuel is conducted from the second pipe.

As shown in greater detail in FIGURE 2, the combustion chamber is formed by an outer casing and a flame tube 31 having outer and inner flame tube walls 32, 33, the inlet end of the combustion chamber, which is closely adjacent to the outlet of thecompressor, being annular and defined between the outer casing 30 and an inner wall 34 supported by the radially inner end of a row of compressor outlet stator blades 6. The flame tube outer wall 32 divides the airflow from the compressor into two annular streams, one flowing over the outside of the flame tube through a duct 35 formed between the wall 32 and the casing 30 and the other flowing into the flame tube. The air inlet to the flame tube is divided into a large number of individual streams by means of fingers 36 which extend transversely across the inlet and serve to produce an even flow of air into the flame tube. The

I outer wall of the flame tube is substantially imperforate,

that is to say the wall is either imperforate over its entire length or provided with only a small number of holes or slits to admit a small quantity of air from the duct 35 sufficient for example to form a protective layer of cooling air over the inner surface of this wall.

At the rearward end of the compressor, the compressor rotor is formed with a rearwardly extending stub shaft 37 which is journalled in the intermediate bearing 17 and rearward of the bearing is provided with splines 38 which engage the forward end of the shaft 14. A truncated conical support member 39 mounted on the stub shaft between the splines and the bearing is provided with a radial flange 40 at its rearward end, and

the fuel disc 24 is held in position on this flange by a second similar support member 41 flanged at 42 which also is mounted on the shaft, the disc being secured be tween the two flanges by bolts 43, and so dimensioned that its periphery, which is spaced from the outer wall of the flame tube, is swept by the annular air stream entering the flame tube. A fuel distributing plug 44 provided with radial passages 45 is threaded into the hollow interior of the stub shaft 37 and is connected to the rear.- ward end of the second fuel pipe 23 so that by way of apertures 46 in the wall of the stub shaft, a path for fuel is formed from the pipe 23 to a space 47 between the support members 39, 41, Radial slots 48 formed in the forward face of the flange 42 allow fuel from the space 47 to flow into an annular trough 49 formed in the rearward face of the disc 24, from which under centrifugal force it spills on to the exposed radially outer portion of the rearward surface of the disc. Thisexposed surface portion is slightly inwardly coned, the

angle which the coned portion of the surface makes with a radial plane being not less than 1 /2 preferably between 3' and 5, so that the fuel is caused to adhere to the disc surface by centrifugal force. as it spreads radially outwards over the disc. 1 Since the rearward or downstream facing surface of the disc forms the up-v separate disc 72 also supported stream boundary wall of the combustion space within the fuel may be carried by the-disc as will produce a sheet of a fuel as distinctfrom a fuel sprayv thrown off centrifugally from the disc'into the incoming high velocity air stream so that a high degree of atomisation is effected.. On'eor more igniters 50 extend through the outer wall of the flame tube within the fuel and air mixing zone downstream of the fuel-carrying disc in which primary combustion takes place. In order to assist combustion of the fuel/air mixture in this primary combustion zone by increasing the natural turbulence ofthe mixture, and thereby produc ng a shortening of the flame length within the flame tube,

paddles 5'1 are mounted for rotation on the rearward face of the fueldisc as shown-m re clearly in FIGURE 3. a The angle whichthese paddles make with a radius of the disc is between about60 and 8 5, preferably in the region of the latter.

The downstream end of the fiarne tube outer wall 32 is corrugated toform 'a number of longitudinally extending chutes 56 which are equally spaced apart circumferentially and ,accordingly'form circumferentially alternatingpassag'es 57, '58 for hot gases from the interior of the flame tube and for secondary air from the duct formed between the outer wall of the flame tube and the casing,

respectively. The chutesextend across the full Width of the combustion chamber outlet but the passages formed.

by the chutes may be subdivided by thin vanes'59 into a number of individualpassages toassist in produ'cingxa smooth gas flow. The sides of the chutes may be parallel, but preferably theyconverge towards the axis of the plant as shown in FIGURE 4.

The inlet guide vanes 19 of the turbine are located across V plied directly on to the surface of the fuel disc.

other modification in which one or more additional sets the combustion chamber outlet path immediately down- URE 5, each chute is so aligned with respect to a turbine inlet guide vane as to cause the secondary .air to flow mainly over the convex: surface of the guide vane, only needed to distribute a thin film of air over the surface for cooling purpose. Some of the secondary air flowing over .the convex surface of a vane gravitates off towards the concave surface of the next adjacent guide vane and in so doing mixes with the combustion gases in the guidevane assa es. B means of this arran ement ood mixing of the secondary air and combustion gases is effected V without destroying the general axial flow of each, and in consequence the pressure losses in mixing are low.

-' V stream of the outletofthe chutes andiasshownin FIG sufficient being directed on to the concave surface as is The inner wall 33 of the fiametube is of hollow construction to provide a passagefitl through the hollow interior of the wall for cooling air, and the radially inner. ends of the secondary air passages 53 are placed in communication with the passage, 69 by means of apertures 62 in the wall 33 at the downstreanrend of the flame tube which form the inlet to the passage so that some of the secondary air is metered into this passage and flowsin the forward directionto an outlet 63 .at the upstream end of the flame tube. A small fan 61 in the form of a centrifugal compressor rotor, is mounted at this'outlet for rotation with the disc 24 to create a region of low pressure at the outlet which serves to draw secondary air through the passage as and to discharge this air into the primary combustion-zone within the flame tube.

FIGURE 6 shows diagrammatically a modification of t a I a 1 on the'shaft '71 is provided, on the downstreamside of the fuel disc, on which turbulence-forming paddles 73 are'carriedQPuel'is admitted to the space between the two discs through apertures 74 in the shaft, and-flows into an annular trough .75

formed in the surface of the disc '70 from whlchit is distributed over thedisc surface. FIGUREId also shows a. modified form of flame tube inlet in which fingers '76 of triangular shape extend radially inwards across this inlet terminating short of the wall 34; by arrangement the airflow adjacent the wall 7 34 is uninterrupted and thus enters the flametube as a truly, annular stream. As shown'in FIGURE ,7, the passages between the fingers 76 are tapered and expand in the radiallyinward direction so that the air flow is metered into the flame tube, increasingin thenradially inward direction. Either or;both of thesefeatures may equally be applicable'to the fingers 36 ,of the first embodiment.

In a further modification, thezfu el conduit in' the 1101-. low shafting may be replaced by'one or more stationary pipes which terminate in nozzles; located near the centre of the fuel-carrying disc from which nozzlesffuel'is sup- In anof rotary paddles are required, for example to increase turbulence in a downstream partof thefiarne tube, at least part of the inner wall of the flame tube may be mounted on the shaft 14 or 71 and such additional paddles may be supported on the rotary portion of thewall. In yet another modification, secondary air Emay be'su'ppliedto the hollow interior of the flame tube inner" wall through pipes which extend through the chutes into the interior of this wall, or alternatively through cooling air ducts formed through the turbine inlet guide vanes it! ,or the shaft14 The present application is a division of copending patentapplicationSerial No. 647,918, filed March 22, 1957, now Patent No. 3,126,705 in the names of the. present applicants.

We claim;

1. Gas turbine plant comprising acompressor, an annular combustion chamberand a turbine; said combustion chamber comprising an annular flame tube having'inner and outer walls, an inletfrom the compressor at one end and an outlet connected to the turbine inlet at the other end, means for supplying fuel to the interior of the flame tube, and an aircasing enclosing said fiametube and definmg with said outer wall thereof an annular duct for conducting air from the compressor to. the turbine inlet; said turbine comprising a row of turbineinlet guide vanes having opposite concave and convex fa'ces; and said flame tube outer'wall being formed at itsidownstream end into longitudinally extending chutes forming circumferentially alternating passages for discharging'streams of air from said annular ductjand combustion gases from said flame tube, the chutes extending to the plane of the turbine inlet and being arranged so that each said stream of air is so aligned with one of? said inlet guide vanes that a small P0111011 of's'aid stream is discharged on to the concave face of the vane and the greater portion .on to the convex face of the vane.

2. Gasturbine plant according, to claim 1 wherein said flame tube outer wall issubstantially imperforate.

3. Gas turbine plantaccording to claim 1 wherein said turbine1, inlet guide vanes are equal in number to said passages for discharging streams of air.

4. Gas turbine plant according to claim 1 wherein said flame tube inner wall is of hollow construction, the hollow interior, thereof having, an inlet at its turbine end in communication with said turbine inlet and connected to receive air'fromsaid annular duct and an outlet at its compressor end opening into the interior of the flame tube.

5.v Gas turbine plant comprising a combustion chamber which includes a flame tube andaductfor air connected to by-pass the flame tube, a turbine, an inlet to said turbine guide vanes in said inlet, each guideivane having one concave face and one convex face, a plurality of longitudinally-extending chutes defining a first set of passages for air flowing from the duct to the turbine and a second set of passages alternating with the passages of said first set for combustion gases flowing from the flame tube to the turbine, each said chute extending to the plane of the turbine inlet being aligned with a separate inlet guide vane of the turbine to discharge a small portion of the air flowing therethrough on to the concave face of the vane and the greater portion of said air on to the convex face of the vane.

References Cited by the Examiner UNITED STATES PATENTS 10 SAMUEL LEVINE, Primary Examiner.

JULIUS E. WEST, Examiner. 

1. GAS TURBINE PLANT COMPRISING A COMPRESSOR, AN ANNULAR COMBUSTION CHAMBER AND A TURBINE; SAID COMBUSTION CHAMBER COMPRISING AN ANNULAR FLAME TUBE HAVING INNER AND OUTER WALLS, AN INLET FROM THE COMPRESSOR AT ONE END AND AN OUTLET CONNECTED TO THE TURBINE INLET AT THE OTHER END, MEANS FOR SUPPLYING FUEL TO THE INTERIOR OF THE FLAME TUBE AND AN AIRCASING ENCLOSING SAID FLAME TUBE AND DEFINING WITH SAID OUTER WALL THEREOF AND ANNULAR DUCT FOR CONDUCTING AIR FROM THE COMPRESSOR TO THE TURBINE INLET; SAID TURBINE COMPRISING A ROW OF TURBINE INLET GUIDE VANES HAVING OPPOSITE CONCAVE AND CONVEX FACES; AND SAID FLAME TUBE OUTER WALL BEING FORMED AT ITS DOWNSTREAM END INTO LONGITUDINAL EXTENDING CHUTES FORMING CIRCUMFERENTIALLY ALTERNATING PASSAGES FOR DISCHARGING STREAMS OF AIR FROM SAID ANNULAR DUCT AND COMBUSTION GASES FROM SAID FLAME TUBE, THE CHUTES EXTENDING TO THE PLANE OF THE TURBINE INLET AND BEING ARRANGED SO THAT EACH SAID STREAM OF AIR IS SO ALIGNED WITH ONE OF SAID INLET GUIDE VANES THAT A SMALL PORTION OF SAID STREAM IS DISCHARGED ON TO THE CONCAVE FACE OF THE VANE AND THE GREATER PORTION ON TO THE CONVEX FACE OF THE VANE. 